This study presents a description of permeability in an active fault zone located in the Great Basin extensional province. The fault hydraulic structure is inferred from geostatistical analysis of temperatures in 143 geothermal springs, located along a fault trace in the Alvord Basin of southeast Oregon. Based on this analysis, we conclude that the fault zone is predominately low permeability, interspersed with relatively few, spatially-discrete, high-permeability channels. The conceptual model presented is in agreement with the findings of other investigators, but extends their work by offering a representation of fault properties at the tens to hundreds of meters scale.